Authorities in Spain and Morocco closed airports Tuesday, as ash from an Icelandic volcano once again disrupts air travel.

Spain's air traffic control agency (Aena) said Tuesday that four airports in the Canary Islands and three airports in southern Spain have been shut down.

Morocco closed several of its airports including Casablanca.

The volcano continued belching ash on Tuesday. Officials say they do not know how long the eruption will continue.

Volcanic activity has shut down sections of European airspace on-and-off for more than a month.

The cloud of abrasive ash can damage aircraft engines and cause other problems for airplanes in flight.

The European Union says airlines lost more than $3 billion when ash from the same volcano crippled air travel across Europe for nearly a week in April.

Some information for this report was provided by AP, AFP and Reuters.